Initial commit

.gitignore

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+node_modules
+.nyc_output
+npm-debug.log
+package-lock.json
+yarn.lock

.travis.yml

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+language: node_js
+node_js:
+  - '8'
+script: npm test
+after_success: npm run coverage
+notifications:
+  email:
+    on_success: never

LICENSE

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+MIT License
+
+Copyright (c) 2018 Luke Childs
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

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+# create-xpub
+
+> Create a BIP32 extended public key
+
+[![Build Status](https://travis-ci.com/lukechilds/create-xpub.svg?branch=master)](https://travis-ci.com/lukechilds/create-xpub)
+[![Coverage Status](https://coveralls.io/repos/github/lukechilds/create-xpub/badge.svg?branch=master)](https://coveralls.io/github/lukechilds/create-xpub?branch=master)
+[![npm](https://img.shields.io/npm/v/create-xpub.svg)](https://www.npmjs.com/package/create-xpub)
+
+## Install
+
+```shell
+npm install create-xpub
+```
+
+## License
+
+MIT © Luke Childs

package.json

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+{
+  "name": "create-xpub",
+  "version": "0.0.0",
+  "description": "Create a BIP32 extended public key",
+  "main": "src/index.js",
+  "engines": {
+    "node": ">=8"
+  },
+  "scripts": {
+    "test": "xo && nyc ava",
+    "coverage": "nyc report --reporter=text-lcov | coveralls"
+  },
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/lukechilds/create-xpub.git"
+  },
+  "keywords": [
+    "xpub",
+    "bip32",
+    "bitcoin",
+    "cryptocurrency"
+  ],
+  "author": "Luke Childs <lukechilds123@gmail.com> (http://lukechilds.co.uk)",
+  "license": "MIT",
+  "bugs": {
+    "url": "https://github.com/lukechilds/create-xpub/issues"
+  },
+  "homepage": "https://github.com/lukechilds/create-xpub#readme",
+  "devDependencies": {
+    "ava": "^0.25.0",
+    "coveralls": "^3.0.2",
+    "nyc": "^13.1.0",
+    "xo": "^0.23.0"
+  },
+  "dependencies": {
+    "bs58check": "^2.1.2",
+    "hash.js": "^1.1.7"
+  }
+}

src/index.js

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+const bs58check = require('bs58check');
+const {sha256, ripemd160} = require('hash.js');
+
+const XPUB = 0x0488B21E;
+
+const compressPublicKey = publicKey => {
+	if (publicKey.startsWith('02') || publicKey.startsWith('03')) {
+		return publicKey;
+	}
+
+	const yIsEven = (parseInt(publicKey.slice(-2), 16) % 2 === 0);
+
+	return (yIsEven ? '02' : '03') + publicKey.slice(2, 66);
+};
+
+const hash160 = buf => ripemd160().update(
+	sha256().update(buf).digest()
+).digest();
+
+const getPublicKeyFingerprint = publicKey => {
+	publicKey = Buffer.from(publicKey, 'hex');
+
+	const publicKeyHash = hash160(publicKey);
+
+	return (
+		((publicKeyHash[0] << 24) |
+      (publicKeyHash[1] << 16) |
+      (publicKeyHash[2] << 8) |
+      publicKeyHash[3]) >>>
+    0
+	);
+};
+
+const createXpub = ({network = XPUB, depth, childnum, chainCode, publicKey}) => {
+	publicKey = compressPublicKey(publicKey);
+	const fingerprint = getPublicKeyFingerprint(publicKey);
+
+	const xpub = Buffer.from([
+		network.toString(16).padStart(8, '0'),
+		depth.toString(16).padStart(2, '0'),
+		fingerprint.toString(16).padStart(8, '0'),
+		childnum.toString(16).padStart(8, '0'),
+		chainCode,
+		publicKey
+	].join(''), 'hex');
+
+	return bs58check.encode(xpub);
+};
+
+module.exports = createXpub;

test/unit.js

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+import test from 'ava';
+import createXpub from '..';
+
+test('createXpub is exported', t => {
+	t.not(createXpub, undefined);
+});